1. Field of the Invention
The invention relates to a heart-rhythm monitoring device for a vehicle, and more particularly, to a device and method for monitoring heart rhythm in a vehicle that reliably determines whether a driver has an arrhythmia while driving the vehicle.
2. Description of the Related Art
Devices for monitoring the cardiac status of a driver are becoming increasingly important in aging societies to prevent traffic accidents that occur as a result of cardiovascular disorder (i.e., heart disease). This is because if an individual at risk of having life-threatening arrhythmia goes into cardiac arrest and loses consciousness while driving, for example, the vehicle driven by that individual is more likely to cause a serious accident.
One device for monitoring the cardiac status of an individual is an electrocardiogram or ECG monitor that measures cardiac electrical activities. In particular, an ambulatory Holter monitoring can record electrocardiogram for 24 hours or more. The fact that the Holter monitor can non-invasively measure cardiac status simply with electrodes attached to the body surface makes it suitable for measuring the cardiac status of a driver.
However, in order for a cardiac abnormality to be confirmed, the electrocardiogram waveforms recorded over a predetermined period of time by the Holter monitor must first be checked by a doctor or other individual with knowledge in that field. The Holter monitor is not designed to predict a cardiac abnormality and automatically take the necessary measures.
On the other hand, Japanese Patent Application Publication No. JP-A-2004-261580, for example, describes a cardiosaver device which is a self-contained implanted device that predicts an acute myocardial infarction (AMI) based on results from monitoring the ST segment of the electrocardiogram waveform and issues an alarm. When a predetermined electrocardiogram waveform is detected, the cardiosaver device transmits a signal that indicates the cardiac status of the individual wearing the device to the wearer and an external medical institution or the like.
However, the cardiosaver device described in Japanese Patent Application Publication No. JP-A-2004-261580 is based on monitoring the ST segment of the electrocardiogram waveform, and is thus cannot be applied to a case where it is difficult to accurately measure the ST segment due to myoelectric noise, or the like, that is produced while driving.